A Study on the Modelling and Controlling of a Smart Grid for Railway Power Supply A Case Study: Ethio-Djibouti Railway Line

Abstract

Power quality analysis is a crucial aspect of managing railway power supply systems. These complex networks must maintain consistent, reliable electricity to power the various components essential for efficient and safe train operations. Analyzing power quality involves closely monitoring a range of electrical parameters, such as voltage, current, frequency, and waveform distortions, to identify any anomalies or deviations from optimal performance. The Ethio Djibouti railway line, a critical transportation link connecting the landlocked nation of Ethiopia to the port city of Djibouti, has been the subject of a comprehensive power quality analysis. This in-depth investigation sought to thoroughly examine the electrical systems and infrastructure supporting this vital rail network, ensuring reliable and efficient operation. Power quality is crucial for any railway, as consistent and stable electricity is required to power the locomotives, signaling systems, and other electrified components. The analysis delved into factors such as voltage regulation, harmonic distortion, power factor, and load balancing across the railway's distribution network. By closely monitoring these parameters, the study was able to identify any inconsistencies, anomalies, or areas for improvement, providing valuable insights to the railway operators. This research delves into investigating power quality phenomena on the Ethiopia-Djibouti railway line, specifically focusing on the Adegala and Aysha 230kV traction substations. Through the utilization of a power quality analyzer, measurements were taken at both 230kV and 25 kV to analyze the harmonic currents, power quantity, and overall distortion of voltage and current. The results of the measurements and simulations point towards exceeding IEEE standard 519-1992 limitations in terms of current and voltage harmonics. Significant voltage imbalances were detected within the train supply network's connecting spot, with the imbalance on the 230kV side surpassing 2%, failing to meet IEEE standard 1159-2009. Considering this, the research focuses on exploring the smart grid integration of wind energy with the railway's power supply. This study examines and maximizes the power generation from wind energy sources using artificial intelligence technique radial basis function network based maximum power point tracking controller to extract maximum power. The proposed MPPT controller design is applied to a 300kW wind energy structure, utilizing a conventional boost converter to maximize power output. The simulation is conducted in MATLAB and integrated with the railway power supply system to evaluate performance. The mean square error (MSE) obtained from the simulation results helps to validate the effectiveness of the control algorithm. Testing the MPPT approach under various wind speeds using MATLAB/Simulink shows promising results, with the system achieving an average maximum power of 289.3 kW at a wind speed of 20 m/sec. The low MSE value of 0.012 indicates the suitability of this MPPT controller for practical applications. The research delves into the intricate relationship between wind energy integration and railway power supply, exploring its viability in both grid-connected and island modes. By harnessing the power of the wind, this innovative approach aims to supplement the energy needs of railway infrastructure, reducing reliance on traditional fossil fuel-based sources and promoting sustainable transportation. In the grid-connected mode, the study analyzes how wind turbines can be seamlessly integrated into the existing power grid, allowing for the bidirectional flow of electricity and ensuring a reliable and uninterrupted supply of power to railway operations. All traction substations connected to the power grid in grid-connected mode are experiencing overload conditions. The recorded bus voltage fluctuates between 239kV and 249.9kV, failing to comply with the IEEE standard, which stipulates an acceptable voltage range of +5% and -5% of the nominal voltage and all traction substations connected to the power grid supply side operate underloaded when in island mode. The bus voltage at the traction load side ranges from 20.71 kV to 26.3 kV, adhering to European standards EN50163: 2004. According to these standards, the maximum non-permanent voltage permitted for short durations is 29 kV, while the minimum permanent voltage must not fall below 19.0 kV. This compliance ensures that the voltage levels remain within safe and efficient operational limits, thereby maintaining the reliability and stability of the traction power system. This research not only addresses the issue of unreliable electricity supply, but it also contributes to the development of railway power systems by introducing renewable energy sources for railway electrification. By incorporating smart grid technology, efficient energy management and utilization can be achieved, ensuring a more reliable and sustainable power supply for the railway line.